CN105315947B

CN105315947B - Adhesive composition and surface protective film

Info

Publication number: CN105315947B
Application number: CN201510195099.XA
Authority: CN
Inventors: 长仓毅; 长谷川良; 吉田弘幸; 菱沼昌世
Original assignee: Fujimori Kogyo Co Ltd
Current assignee: Fujimori Kogyo Co Ltd
Priority date: 2014-07-03
Filing date: 2015-04-22
Publication date: 2023-02-17
Anticipated expiration: 2035-04-22
Also published as: KR101782513B1; KR101782491B1; JP6243300B2; KR20170092495A; KR101887355B1; CN105315947A; TW201602277A; JP2016014118A; TW201936853A; KR20160004906A; TWI718549B; KR20170110561A; TWI665277B

Abstract

The invention provides an adhesive composition and a surface protective film which have a long pot life and a high crosslinking speed without using an organic tin compound. The adhesive composition contains (C) 0.1-10 parts by weight of a bifunctional or higher isocyanate compound, (D) 0.001-0.5 parts by weight of a crosslinking catalyst for a metal chelate, and (E) 0.1-300 parts by weight of a keto-enol tautomer compound, per 100 parts by weight of a copolymer of (A) at least one (meth) acrylate monomer having an alkyl group and having 4-18 carbon atoms, and (B) a hydroxyl group-containing copolymerizable monomer, and has a (E)/(D) weight ratio of 70-1000.

Description

Adhesive composition and surface protective film

Technical Field

The present invention relates to an adhesive composition and a surface protective film. More specifically, the present invention relates to a binder composition and a surface protective film which have a long pot life and a high crosslinking rate without using an organotin compound, and which are obtained by using a crosslinking catalyst of a metal chelate compound other than an organotin compound, because the use of an organotin compound which has an adverse effect on the environment has been recently restricted.

Background

From the viewpoint of excellent transparency, an acrylic adhesive comprising a copolymer obtained by copolymerizing an alkyl (meth) acrylate as a main component and an acrylic monomer having a hydroxyl group, a carboxyl group, or the like as a functional group is preferably used for the adhesive composition for optical use. In addition, an adhesive agent is required to appropriately adjust various physical properties such as adhesive force of the adhesive agent layer. In particular, in order to be suitable for a production process in a factory, an adhesive layer for a surface protective film is required to be suitable for bonding by an automatic bonding apparatus and to have an excellent balance of adhesive force at a low peeling speed and a high peeling speed. In addition, there is a need for a binder composition having excellent physical properties such as long shelf life in addition to balance of adhesive strength.

Such a method for adjusting various physical properties of the adhesive layer can be performed by adjusting the adhesive force, cohesive force, and the like by performing a crosslinking reaction using an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, or the like that reacts with a functional group such as a hydroxyl group, a carboxyl group, or the like contained in the acrylic adhesive composed of the copolymer.

Conventionally, isocyanate-based crosslinking agents have been generally used as crosslinking agents for acrylic adhesives. In addition, in the crosslinking reaction using an isocyanate-based crosslinking agent, a metal chelate is often used as a catalyst for accelerating the crosslinking reaction.

Generally, dibutyltin dilaurate, which is an organotin compound, is used as a catalyst for the crosslinking reaction from the viewpoint of excellent reaction rate of the crosslinking reaction, but the use of dibutyltin compounds has been avoided at present because of their harmful toxicity.

Therefore, a crosslinking catalyst which can be used in combination with an isocyanate-based crosslinking agent, is inexpensive and has an excellent reaction rate of crosslinking reaction as a substitute for dibutyltin compounds is required, but it is difficult to develop and obtain the catalyst.

In view of such circumstances, patent document 1 discloses the following: as a crosslinking catalyst which can be used in combination with an isocyanate-based crosslinking agent, an iron chelate compound is preferable among metal chelate compounds; and is particularly preferable because of its excellent catalytic activity.

However, the acrylic adhesive composition containing the crosslinking catalyst slowly undergoes a crosslinking reaction even during standing at normal temperature. Therefore, in the industrial production of adhesives, a crosslinking catalyst and a reaction inhibitor are generally used together to stop a crosslinking reaction after mixing raw materials of an adhesive composition until the crosslinking reaction starts.

Regarding the combined use of the crosslinking catalyst and the reaction inhibitor, patent document 2 discloses a method for producing a polyurethane, wherein a reaction polyurethane mixture is used, the reaction polyurethane mixture containing a catalyst system comprising a mixture of at least one metal acetylacetone and acetylacetone, and the weight ratio of the metal acetylacetone to the acetylacetone is 2.

The binder composition described in patent document 1 proposes the amount of a metal compound (crosslinking catalyst) added to a copolymer containing a hydroxyl group and a carboxyl group and having a (meth) acrylate as a constituent monomer unit, but does not describe the amount of a crosslinking inhibitor added. Patent document 1 describes a method of using a reaction inhibitor, a method of adding a solvent that suppresses an increase in viscosity, a method of using a crosslinking agent that blocks a functional group (block) such as a block isocyanate, and the like, as a method of suppressing the increase in viscosity after the crosslinking agent is mixed in the adhesive composition, but the method is not specifically described.

Further, patent document 2 discloses a method for producing a polyurethane using a catalyst system containing: even with the use of a metal acetylacetone catalyst of iron, copper, etc., which is very highly active at low temperatures, metal acetylacetone and acetylacetone which do not cause early curing and have excellent stability and good catalytic activity are used.

However, in the method described in patent document 2, the weight ratio of metal acetylacetone to acetylacetone is set to 2.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 2011-001440

Patent document 2: japanese patent laid-open No. 2008-285681

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive composition and a surface protective film which have a long pot life and a high crosslinking speed without using an organotin compound.

Means for solving the problems

In order to solve the above problems, the present invention provides an adhesive composition comprising, per 100 parts by weight of a copolymer of (a) at least one (meth) acrylate monomer having an alkyl group and having 4 to 18 carbon atoms and (B) a hydroxyl group-containing copolymerizable monomer as a copolymerizable monomer group, (C) 0.1 to 10 parts by weight of a bifunctional or higher isocyanate compound, (D) 0.001 to 0.5 parts by weight of a metal chelate crosslinking catalyst, and (E) 0.1 to 300 parts by weight of a keto-enol tautomer compound, wherein the ratio of (E)/(D) by weight is 70 to 1000.

It is preferable that the viscosity of the adhesive composition after storage at 23 ℃ for 8 hours after the adhesive composition is blended is less than 1.25 times the viscosity immediately after the blending.

Further, it is preferable that the hydroxyl group-containing copolymerizable monomer (B) is at least one selected from the group consisting of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-methylol (meth) acrylamide and N-hydroxyethyl (meth) acrylamide.

Among the difunctional or higher isocyanate compounds of the above (C), the difunctional isocyanate compound is preferably a compound which is produced by reacting a non-cyclic aliphatic isocyanate compound with a diol compound. The diisocyanate compound is an aliphatic diisocyanate, and is preferably one selected from the group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. The diol compound is preferably one selected from the group consisting of 2-methyl-1, 3-propanediol, 2-dimethyl-1, 3-propanediol, 2-methyl-2-propyl-1, 3-propanediol, 2-ethyl-2-butyl-1, 3-propanediol, 3-methyl-1, 5-pentanediol, 2-dimethyl-1, 3-propanediol monohydroxypivalate, polyethylene glycol, and polypropylene glycol.

In the (C) di-or higher-functional isocyanate compound, the tri-functional isocyanate compound is preferably at least one compound selected from the group consisting of isocyanurate of hexamethylene diisocyanate compound, isocyanurate of isophorone diisocyanate compound, adduct of hexamethylene diisocyanate compound, adduct of isophorone diisocyanate compound, biuret of hexamethylene diisocyanate compound, biuret of isophorone diisocyanate compound, isocyanurate of toluene diisocyanate compound, isocyanurate of xylylene diisocyanate compound, isocyanurate of hydrogenated xylylene diisocyanate compound, adduct of toluene diisocyanate compound, adduct of xylylene diisocyanate compound and adduct of hydrogenated xylylene diisocyanate compound.

In the adhesive composition, it is preferable that the crosslinking catalyst does not contain an organotin compound.

The copolymer is preferably an acrylic polymer containing at least one or more of a carboxyl group-containing monomer and a nitrogen-containing vinyl monomer containing no hydroxyl group as another copolymerizable monomer group.

The gel fraction of the adhesive composition after crosslinking is preferably 90 to 100%.

In addition, the adhesive layer obtained by crosslinking the adhesive composition preferably has an adhesive strength of 0.05 to 0.2N/25mm at a low peeling speed of 0.3m/min and an adhesive strength of 2.0N/25mm or less at a high peeling speed of 30 m/min.

The present invention also provides an adhesive film comprising a resin film and an adhesive layer formed on one or both surfaces of the resin film, wherein the adhesive layer is formed by crosslinking the adhesive composition.

The present invention also provides a surface protective film comprising a resin film and, formed on one surface thereof, an adhesive layer formed by crosslinking the adhesive composition.

The surface protective film of the present invention can be used for the purpose of a surface protective film for a polarizing plate.

The surface protective film of the present invention can be used for the purpose of protecting the surface of a precision electric/electronic component selected from the group consisting of a flexible printed wiring board, a rigid printed wiring board, and a transparent conductive film.

Effects of the invention

The present invention can provide an adhesive composition and a surface protective film which have a long pot life and a high crosslinking speed without using an organotin compound.

In addition, the adhesive composition according to the present invention does not contain a toxic organic tin compound, and therefore, is highly safe.

Detailed Description

The present invention will be described below based on preferred embodiments.

The adhesive composition of the present invention is characterized by containing 0.1 to 10 parts by weight of (C) a bifunctional or higher isocyanate compound, (D) 0.001 to 0.5 parts by weight of a metal chelate crosslinking catalyst, and (E) 0.1 to 300 parts by weight of a keto-enol tautomer compound, per 100 parts by weight of a copolymer of (A) at least one (meth) acrylate monomer having an alkyl group and having 4 to 18 carbon atoms, and (B) a hydroxyl group-containing copolymerizable monomer, and by having a (E)/(D) weight ratio of 70 to 1000.

Examples of the (meth) acrylate monomer having an alkyl group and having 4 to 18 carbon atoms include: butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, myristyl (meth) acrylate, isomyristyl (meth) acrylate, cetyl (meth) acrylate, isohexadecyl (meth) acrylate, stearyl (meth) acrylate, and the like.

The content of the (meth) acrylate monomer having an alkyl group and a carbon number of C4 to C18 (A) is preferably 50 to 98 parts by weight based on 100 parts by weight of the copolymer.

Examples of the (B) hydroxyl group-containing copolymerizable monomer include: hydroxyalkyl (meth) acrylates such as 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate; hydroxyl group-containing (meth) acrylamides such as N-hydroxy (meth) acrylamide, N-methylol (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide.

Preferably, the hydroxyl group-containing copolymerizable monomer is at least one member selected from the group consisting of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-methylol (meth) acrylamide and N-hydroxyethyl (meth) acrylamide.

The content of the hydroxyl group-containing copolymerizable monomer (B) is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the copolymer.

The copolymer may further contain at least one or more of a carboxyl group-containing monomer, a hydroxyl group-free nitrogen-containing vinyl monomer, and a polyalkylene glycol mono (meth) acrylate monomer as another copolymerizable monomer group.

It is preferable that the carboxyl group-containing monomer is at least one selected from the group consisting of (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethylhexahydrophthalic acid, 2- (meth) acryloyloxypropylhexahydrophthalic acid, 2- (meth) acryloyloxyethylphthalic acid, 2- (meth) acryloyloxyethylsuccinic acid, 2- (meth) acryloyloxyethylmaleic acid, carboxypolycaprolactone mono (meth) acrylate, and 2- (meth) acryloyloxyethyltetrahydrophthalic acid.

When the aforementioned copolymer includes a carboxyl group-containing monomer as the other copolymerizable monomer group, the content of the carboxyl group-containing monomer is preferably 0.1 to 1.0 part by weight relative to 100 parts by weight of the aforementioned copolymer. The copolymer may not contain the carboxyl group-containing monomer.

The polyalkylene glycol mono (meth) acrylate monomer may be any compound as long as one of a plurality of hydroxyl groups of the polyalkylene glycol is esterified to a (meth) acrylate. Since the (meth) acrylate group is a polymerizable group, it can be copolymerized with a copolymer of the main agent. The other hydroxyl group may be in the state of OH, an alkyl ether such as methyl ether or ethyl ether, or a saturated carboxylic acid ester such as acetic ester.

Examples of the alkylene group of the polyalkylene glycol include an ethylene group (vinyl group), a propylene group (propenyl group), and a butylene group (butenyl group), but are not limited thereto. The polyalkylene glycol may be a copolymer of two or more polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol. Examples of the copolymer of polyalkylene glycol include polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, and polyethylene glycol-polypropylene glycol-polybutylene glycol, and the copolymer may be a block copolymer or a random copolymer.

The average number of repetitions of the alkylene oxide (alkylene oxide) constituting the polyalkylene glycol chain in the polyalkylene glycol mono (meth) acrylate monomer is preferably 3 to 14. The "average number of repetitions of alkylene oxide" means the average number of repetitions of alkylene oxide units in the "polyalkylene glycol chain" moiety contained in the molecular structure of the aforementioned polyalkylene glycol mono (meth) acrylate monomer.

The polyalkylene glycol mono (meth) acrylate monomer is preferably at least one selected from the group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate.

More specifically, there may be mentioned: polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polybutylene glycol mono (meth) acrylate, polyethylene glycol polypropylene glycol mono (meth) acrylate, polyethylene glycol polybutylene glycol mono (meth) acrylate, polypropylene glycol polybutylene glycol mono (meth) acrylate, polyethylene glycol polypropylene glycol polybutylene glycol mono (meth) acrylate; methoxy polyethylene glycol- (meth) acrylate, methoxy polypropylene glycol- (meth) acrylate, methoxy polybutylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polypropylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, methoxy-polypropylene glycol-polybutylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol- (meth) acrylate; ethoxy polyethylene glycol- (meth) acrylate, ethoxy polypropylene glycol- (meth) acrylate, ethoxy polybutylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polypropylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, ethoxy-polypropylene glycol-polybutylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol- (meth) acrylate, and the like.

The content of the polyalkylene glycol mono (meth) acrylate monomer is preferably 0 to 50 parts by weight relative to 100 parts by weight of the copolymer. The copolymer may not contain the polyalkylene glycol mono (meth) acrylate monomer.

Examples of the nitrogen-containing vinyl monomer containing no hydroxyl group include: vinyl monomers containing an amide bond, vinyl monomers containing an amino group, vinyl monomers having a nitrogen-containing heterocyclic structure, and the like. More specifically, there may be mentioned: cyclic nitrogen vinyl compounds having an N-vinyl-substituted heterocyclic structure such as N-vinyl-2-pyrrolidone, N-vinylpyrrolidone, methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, and N-vinyllaurolactam; cyclic nitrogen vinyl compounds having an N- (meth) acryloyl-substituted heterocyclic structure such as N- (meth) acryloyl morpholine, N- (meth) acryloyl piperazine, N- (meth) acryloyl aziridine, N- (meth) acryloyl azetidine, N- (meth) acryloyl pyrrolidine, N- (meth) acryloyl piperidine, N- (meth) acryloyl azepane, and N- (meth) acryloyl azocane; cyclic nitrogen vinyl compounds having a heterocyclic structure containing a nitrogen atom and a vinyl-based unsaturated bond in the ring, such as N-cyclohexylmaleimide and N-phenylmaleimide; unsubstituted or monoalkyl-substituted (meth) acrylamides such as (meth) acrylamide, N-methyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N-tert-butyl (meth) acrylamide; dialkyl-substituted (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-dipropylacrylamide, N-diisopropyl (meth) acrylamide, N-dibutyl (meth) acrylamide, N-ethyl-N-methyl (meth) acrylamide, N-methyl-N-propyl (meth) acrylamide, and N-methyl-N-isopropyl (meth) acrylamide; n, N-dimethylaminomethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, N-dimethylaminopropyl (meth) acrylate, N-dimethylaminoisopropyl (meth) acrylate, N-dimethylaminobutyl (meth) acrylate, N-diethylaminomethyl (meth) acrylate, N, dialkylamino (meth) acrylates such as N-diethylaminoethyl (meth) acrylate, N-ethyl-N-methylaminoethyl (meth) acrylate, N-methyl-N-propylaminoethyl (meth) acrylate, N-methyl-N-isopropylaminoethyl (meth) acrylate, N-dibutylaminoethyl (meth) acrylate, and tert-butylaminoethyl (meth) acrylate; n, N-dialkyl-substituted aminopropyl (meth) acrylamides such as N, N-dimethylaminopropyl (meth) acrylamide, N-diethylaminopropyl (meth) acrylamide, N-dipropylaminopropyl (meth) acrylamide, N-diisopropylaminopropyl (meth) acrylamide, N-ethyl-N-methylaminopropyl (meth) acrylamide, N-methyl-N-propylaminopropyl (meth) acrylamide, and N-methyl-N-isopropylaminopropyl (meth) acrylamide; n-vinylcarboxylic acid amides such as N-vinylformamide, N-vinylacetamide, and N-vinyl-N-methylacetamide; (meth) acrylamides such as N-methoxymethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide, and N, N-methylenebis (meth) acrylamide; unsaturated carboxylic acid nitriles such as (meth) acrylonitrile; and so on.

The content of the hydroxyl group-free and nitrogen-containing vinyl monomer is preferably 0 to 20 parts by weight based on 100 parts by weight of the copolymer. The copolymer may not contain the nitrogen-containing vinyl monomer containing no hydroxyl group.

The (C) bifunctional or higher isocyanate compound may be at least one or two or more selected from polyisocyanate compounds having at least two or more isocyanate (NCO) groups in one molecule. The polyisocyanate compound includes aliphatic isocyanates, aromatic isocyanates, acyclic isocyanates, alicyclic isocyanates and the like, and any of these may be used in the present invention. Specific examples of the polyisocyanate compound include: aliphatic isocyanate compounds such as Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), and trimethylhexamethylene diisocyanate (TMDI); aromatic isocyanate compounds such as diphenylmethane diisocyanate (MDI), xylylene Diisocyanate (XDI), hydrogenated xylylene diisocyanate (H6 XDI), dimethyldiphenylene diisocyanate (TOID), and Toluene Diisocyanate (TDI).

Examples of the trifunctional or higher isocyanate compound include: a biuret-modified product or an isocyanurate-modified product of a difunctional isocyanate compound (a compound having two NCO groups in one molecule), and an adduct (a polyol-modified product) of a trivalent or higher polyol (a compound having at least three OH groups in one molecule) such as Trimethylolpropane (TMP) or glycerin.

As the (C) di-or higher-functional isocyanate compound, (C-1) trifunctional isocyanate compound alone or (C-2) difunctional isocyanate compound alone may be used. Further, (C-1) a trifunctional isocyanate compound and (C-2) a difunctional isocyanate compound may be used in combination.

The (C-1) trifunctional isocyanate compound used in the present invention preferably includes at least one or more selected from the group consisting of (C-1-1) first aliphatic isocyanate compounds, and at least one or more selected from the group consisting of (C-1-2) second aromatic isocyanate compounds, wherein the (C-1-1) first aliphatic isocyanate compounds are composed of isocyanurates of hexamethylene diisocyanate compounds, isocyanurates of isophorone diisocyanate compounds, adducts of hexamethylene diisocyanate compounds, adducts of isophorone diisocyanate compounds, biurets of hexamethylene diisocyanate compounds, and biurets of isophorone diisocyanate compounds; the (C-1-2) second aromatic isocyanate compound group is composed of isocyanurate of tolylene diisocyanate compound, isocyanurate of xylylene diisocyanate compound, isocyanurate of hydrogenated xylylene diisocyanate compound, adduct of tolylene diisocyanate compound, adduct of xylylene diisocyanate compound, and adduct of hydrogenated xylylene diisocyanate compound. It is preferable to use (C-1-1) the first aliphatic isocyanate compound group and (C-1-2) the second aromatic isocyanate compound group in combination. In the present invention, the balance of the adhesive strength in the low-speed peeling region and the high-speed peeling region can be further improved by using at least one or more selected from the group consisting of (C-1-1) first aliphatic isocyanate compounds and at least one or more selected from the group consisting of (C-1-2) second aromatic isocyanate compounds in combination as the (C-1) trifunctional isocyanate compounds.

The (C-1) trifunctional isocyanate compound preferably contains at least one member selected from the group consisting of the (C-1-1) first aliphatic isocyanate compounds and at least one member selected from the group consisting of the (C-1-2) second aromatic isocyanate compounds, and the total amount thereof is preferably 0.5 to 5.0 parts by weight based on 100 parts by weight of the copolymer. Further, the mixing ratio of at least one or more selected from the group consisting of (C-1-1) first aliphatic isocyanate compounds and at least one or more selected from the group consisting of (C-1-2) second aromatic isocyanate compounds is preferably (C-1-1) to (C-1-2) in the range of 10% to 90% to 10% by weight.

The (C-2) difunctional isocyanate compound used in the present invention is preferably a compound which is a non-cyclic aliphatic isocyanate compound and is produced by reacting a diisocyanate compound with a diol compound.

For example, when the general formula "O = C = N-X-N = C = O" (where X is a 2-valent group) represents a diisocyanate compound and the general formula "HO-Y-OH" (where Y is a 2-valent group) represents a diol compound, examples of the compound produced by the reaction of the diisocyanate compound and the diol compound include a compound represented by the following general formula Z.

[ general formula Z ]

O＝C＝N-X-(NH-CO-O-Y-O-CO-NH-X) _n -N＝C＝O

Here, n is an integer of 0 or more. When N is 0, the general formula Z is represented as "O = C = N-X-N = C = O". The bifunctional acyclic aliphatic isocyanate compound may include a compound of the general formula Z in which n is 0 (i.e., a diisocyanate compound that does not react with the diol compound), and preferably includes a compound containing n as an essential component, an integer of 1 or more. The difunctional non-cyclic aliphatic isocyanate compound may also be a mixture of a plurality of compounds of the formula Z in which n is different.

The diisocyanate compound represented by the general formula "O = C = N-X-N = C = O" is an aliphatic diisocyanate. Preferably, X is a non-cyclic aliphatic 2-valent group. The aliphatic diisocyanate is preferably composed of one or more compounds selected from the group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

The diol compounds of the formula "HO-Y-OH" are aliphatic diols. Preferably, Y is a non-cyclic aliphatic 2-valent group. The diol compound is preferably composed of one or more compounds selected from the group consisting of 2-methyl-1, 3-propanediol, 2-dimethyl-1, 3-propanediol, 2-methyl-2-propyl-1, 3-propanediol, 2-ethyl-2-butyl-1, 3-propanediol, 3-methyl-1, 5-pentanediol, 2-dimethyl-1, 3-propanediol monohydroxypivalate, polyethylene glycol, and polypropylene glycol.

The weight ratio (C-1/C-2) of the (C-1) trifunctional isocyanate compound to the (C-2) difunctional isocyanate compound is preferably 1 to 90. The amount of the difunctional or higher isocyanate compound (C) is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the copolymer.

In the case of using a polyisocyanate compound as a crosslinking agent,

when a polyisocyanate compound is used as the crosslinking agent, (D) a crosslinking catalyst of the metal chelate compound may be any one which functions as a catalyst for the reaction (crosslinking reaction) between the copolymer and the crosslinking agent, and examples thereof include: and amine compounds such as tertiary amines, metal chelates, organic tin compounds, organic lead compounds, and organic zinc compounds. In the present invention, a metal chelate is used as a crosslinking catalyst.

The metal chelate is a compound in which one or more polydentate ligands L are bonded to a central metal atom M. The metal chelate may or may not have one or more monodentate ligands X bonded to the metal atom M. For example, a metal chelate compound having M as one metal atom has the formula M (L) _m (X) _n When expressed, m is not less than 1, and n is not less than 0. When m is 2 or more, m L's may be the same ligand or different ligands. When n is 2 or more, n X's may be the same ligand or different ligands.

Examples of the metal atom M include Fe, ni, mn, cr, V, ti, ru, zn, al, zr, sn and the like.

Examples of the polydentate ligand L include: beta-keto esters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oil acetoacetate, lauryl acetoacetate, and stearyl acetoacetate; beta-diketones such as acetylacetone (also known as 2, 4-pentanedione), 2, 4-hexanedione, and benzoylacetone. These are keto-enol tautomer compounds, and in the polydentate ligand L, enolates (e.g., acetylacetonates) obtained by deprotonating enols may be used.

Examples of the monodentate ligand X include a halogen atom such as a chlorine atom or a bromine atom, an acyloxy group such as a pentanoyl group, a hexanoyl group, a 2-ethylhexanoyl group, an octanoyl group, a nonanoyl group, a decanoyl group, a selenoyl group, or a stearoyl group, and an alkoxy group such as a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, or a butoxy group.

Specific examples of the metal chelate compound include: tris (2, 4-pentanedionato) iron (III), iron triacetylacetonate, titanium triacetylacetonate, ruthenium triacetylacetonate, zinc diacetoacetonate, aluminum triacetylacetonate, zirconium tetraacetoacetonate, iron (III) tris (2, 4-hexanedionato), zinc bis (2, 4-hexanedionato), titanium tris (2, 4-hexanedionato), aluminum tris (2, 4-hexanedionato), zirconium tetrakis (2, 4-hexanedionato), and the like.

As the organotin compound, there may be mentioned: dialkyl tin oxides, fatty acid salts of dialkyl tin, fatty acid salts of stannous, and the like. Conventionally, dibutyltin compounds have been used in many cases, but in recent years, the problem of toxicity of organotin compounds has been pointed out, and particularly tributyltin (TBT) contained in dibutyltin compounds is also concerned as an endocrine interferon. From the viewpoint of safety, long-chain alkyl tin compounds such as dioctyltin compounds are preferred. Specific examples of the organotin compound include dioctyltin oxide and dioctyltin dilaurate. Although a Sn compound may be used temporarily, in view of the trend of using a substance with higher safety in the future, it is preferable to use a metal chelate compound of Al, ti, fe, or the like, which is higher in safety than Sn.

The metal chelate compound in the binder composition of the present invention preferably contains at least one selected from the group consisting of an aluminum chelate compound, a titanium chelate compound and an iron chelate compound.

The content of the crosslinking catalyst of the metal chelate (D) is preferably 0.001 to 0.5 part by weight based on 100 parts by weight of the copolymer.

As (E) keto-enol tautomer compounds, there may be mentioned: beta-keto esters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oil acetoacetate, lauryl acetoacetate, and stearyl acetoacetate; beta-diketones such as acetylacetone, 2, 4-hexanedione, and benzoylacetone. In the adhesive composition containing a polyisocyanate compound as a crosslinking agent, the isocyanate group of the crosslinking agent is blocked, whereby an excessive increase in the viscosity of the adhesive composition or gelation of the adhesive composition after the crosslinking agent is blended can be suppressed, and the pot life of the adhesive composition can be prolonged.

The content of (E) the keto-enol tautomer compound is preferably 0.1 to 300 parts by weight relative to 100 parts by weight of the copolymer.

In contrast to (D) the crosslinking catalyst of the metal chelate, the (E) keto-enol tautomer compound has an effect of inhibiting crosslinking, and therefore, it is preferable to appropriately set the ratio of the (E) keto-enol tautomer compound to the crosslinking catalyst of the (D) metal chelate. In order to prolong the pot life of the binder composition and improve the storage stability, it is preferable that the ratio by weight of the crosslinking catalyst of (E) keto-enol tautomer compound/(D) metal chelate compound (E)/(D) is high. The value of (E)/(D) is preferably in the range of 70 to 1000, more preferably 70 to 800, most preferably 80 to 600.

More specifically, the viscosity of the adhesive composition after the adhesive composition is blended and stored at 23 ℃ for 8 hours is preferably lower than 1.25 times the viscosity immediately after the blending. This makes it possible to obtain an adhesive composition in which an increase in viscosity after blending is suppressed.

The adhesive composition of the present invention may contain, as additives, an antistatic agent, a polyether siloxane compound, and other conventional antioxidants.

Examples of the antistatic agent include an antistatic agent contained in the binder composition and an antistatic agent copolymerized in the copolymer. The content of the antistatic agent is preferably 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer.

The antistatic agent has a melting point of 25 to 50 ℃ and is preferably an ionic compound which is solid at a temperature of 25 ℃ and/or an ionic compound containing an acryloyl group. These antistatic agents are presumed to have high affinity with acrylic copolymers because of their low melting points and long-chain alkyl groups.

The ionic compound having a melting point of 25 to 50 ℃ is an ionic compound having a cation and an anion, and examples thereof include: the cation is nitrogen-containing onium cation such as pyridinium cation, imidazolium cation, pyrimidinium cation, pyrazolium cation, pyrrolium cation, and ammonium cation, or phosphonium cation and sulfonium cation, and the anion is hexafluorophosphate (PF) ₆ ^- ) Thiocyanate radical (SCN) ^- ) Alkyl benzene sulfonate (RC) ₆ H ₄ SO ₃ ^- ) Perchlorate (ClO) ^4- ) Tetrafluoroborate (BF) ₄ ^- ) And bis (fluorosulfonyl) imide (FSI), bis (trifluoromethanesulfonyl) imide (TFSI), trifluoromethanesulfonate (TF), and the like. Preferably, the compound is a solid at room temperature (e.g., 25 ℃) and can have a melting point of 25 to 50 ℃ by selecting the chain length of the alkyl group, the position of the substituent, the number of the substituents, and the like. The cation is preferably a quaternary azonium cation, and there may be mentioned: quaternary pyridinium cations such as 1-alkylpyridinium (the carbon atoms at the 2-to 6-positions may or may not have a substituent), quaternary imidazolium cations such as 1, 3-dialkylimidazolium (the carbon atoms at the 2-, 4-, and 5-positions may or may not have a substituent), quaternary ammonium cations such as tetraalkylammonium, and the like.

The content of the ionic compound having a melting point of 25 to 50 ℃ is preferably 0.05 to 5 parts by weight relative to 100 parts by weight of the copolymer.

The ionic compound having an acryloyl group may have a cation and an anionMention is made of: the cation is (meth) acryloyloxyalkyltrialkylammonium (R) ₃ N ⁺ -C _n H _2n -OCOCQ＝CH ₂ Wherein Q = H or CH ₃ And R = alkyl), and the like; the anion being phosphate hexafluoride (PF) ₆ ^- ) Thiocyanate (SCN) ^- ) Organic sulfonate (RSO) ₃ ^- ) Perchlorate (ClO) ₄ ^- ) Boron tetrafluoride (BF) ₄ ^- ) And an imide group (R) containing F ^F ₂ N ^- ) And the like, inorganic or organic anions. As F-containing imide radical (R) ^F ₂ N ^- ) R of (A) to (B) ^F Examples thereof include a perfluoroalkylsulfonyl group and a fluorosulfonyl group such as a trifluoromethanesulfonyl group and a pentafluoroethanesulfonyl group. Examples of the imide group containing F include bis (fluorosulfonyl) imide group [ (FSO) ₂ ) ₂ N ^- Bis (trifluoromethanesulfonyl) imide group [ (CF) ₃ SO ₂ ) ₂ N ^- Bis (pentafluoroethanesulfonyl) imide group [ (C) ₂ F ₅ SO ₂ ) ₂ N ^- And the like are described.

The copolymerization amount of the acryloyl group-containing ionic compound in the copolymer is preferably 0.1 to 5.0% by weight.

Specific examples of the antistatic agent are not particularly limited, but specific examples of the ionic compound having a melting point of 25 to 50 ℃ include 1-octylpyridinium hexafluorophosphate, 1-nonylphenium hexafluorophosphate, 2-methyl-1-dodecylpyridinium hexafluorophosphate, 1-octylpyridinium dodecylbenzene sulfonate, 1-dodecylpyridinium thiocyanate, 1-dodecylpyridinium dodecylbenzene sulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate, quaternary ammonium salts of trifluoromethanesulfonic acid, and the like. Further, as a specific example of the ionic compound having an acryloyl group, methyl dimethylaminoacrylate methyl hexafluorophosphate [ (CH) can be mentioned ₃ ) ₃ N ⁺ CH ₂ OCOCQ＝CH ₂ ·PF ₆ ^- Wherein Q = H or CH ₃ 〕、Dimethylamino Ethyl (meth) acrylate bis (trifluoromethanesulfonyl) imide methyl salt [ (CH) ₃ ) ₃ N ⁺ (CH ₂ ) ₂ OCOCQ＝CH ₂ ·(CF ₃ SO ₂ ) ₂ N ^- Wherein Q = H or CH ₃ Dimethylaminomethylmethacrylate bis (fluorosulfonyl) imide methyl salt [ (CH ] ₃ ) ₃ N ⁺ CH ₂ OCOCQ＝CH ₂ ·(FSO ₂ ) ₂ N ^－ Wherein Q = H or CH ₃ And the like.

The aforementioned polyether-modified silicone compound is a silicone compound having a polyether group, except for the usual silicone unit (-SiR) ¹ ₂ -O-) and a siloxane unit (-SiR) comprising a polyether group ¹ (R ² O(R ³ O) _n R ⁴ ) -O-). Herein, R is ¹ Represents one or more alkyl or aryl groups, R ² And R ³ Represents one or more alkylene groups, R ⁴ Represents one or two or more kinds of alkyl groups, acyl groups, etc. (terminal groups). Examples of polyether groups include: polyoxyethylene group ((C) ₂ H ₄ O) _n ) Or polyoxypropylene ((C) ₃ H ₆ O) _n ) And the like.

The polyether-modified silicone compound is preferably a polyether-modified silicone compound having an HLB value of 7 to 15. The polyether-modified silicone compound is preferably contained in an amount of 0.01 to 1.0 part by weight based on 100 parts by weight of the copolymer. More preferably 0.1 to 0.5 parts by weight.

The HLB is a hydrophilic-lipophilic balance (ratio of hydrophilicity to lipophilicity) defined in JIS K3211 (surfactant).

The aforementioned polyether-modified siloxane compound can be obtained, for example, by the following method: an organic compound having an unsaturated bond and a polyoxyalkylene group is grafted to the main chain of a polyorganosiloxane having a silane group by a hydrosilylation reaction. Specifically, there may be mentioned: dimethylsiloxane-methyl (polyoxyethylene) siloxane copolymers, dimethylsiloxane-methyl (polyoxyethylene) siloxane-methyl (polyoxypropylene) siloxane copolymers, dimethylsiloxane-methyl (polyoxypropylene) siloxane copolymers, and the like.

By blending the polyether-modified silicone compound with the adhesive composition, the adhesive strength and reworkability of the adhesive can be improved. When the adhesive composition does not contain the polyether-modified siloxane compound, the cost can be made lower.

Examples of the antioxidant include hindered phenol antioxidants, polyphenol compounds, tocopherol compounds, and the like. Among them, a tocopherol compound is preferable. The tocopherol compound is usually vitamin E, also a chemical substance from natural sources. Therefore, the composition has little adverse effect on human bodies, high safety in use and no pollution to the environment. Further, since it is oil-soluble and is liquid at ordinary temperature, it is also excellent in compatibility with the binder composition and in precipitation resistance. The storage stability of the binder is improved by blending a tocopherol compound as the antioxidant, and therefore, the pot life of the binder composition blended with the curing agent is improved.

The tocopherol compound used in the present invention is preferably a compound having a phenolic hydroxyl group, such as an ester, without converting the phenolic hydroxyl group of tocopherol into a phenolic hydroxyl group, from the viewpoint of being used by being incorporated in a binder composition (not being metabolized as in a human body). Examples thereof include tocopherol and tocotrienol. It is known that tocopherol and tocotrienol are distinguished by a natural compound (d-isomer), a non-natural compound (l-isomer), a racemic body (dl-isomer) of an equivalent mixture thereof, and the like. The natural compound (d-form) and the racemic body (dl-form) are preferable because they can be used as food additives.

Specific examples of the tocopherol compound include at least one compound selected from the group consisting of d- α -tocopherol, dl- α -tocopherol, d- β -tocopherol, dl- β -tocopherol, d- γ -tocopherol, dl- γ -tocopherol, d- δ -tocopherol, dl- δ -tocopherol, d- α -tocotrienol, dl- α -tocotrienol, d- β -tocotrienol, dl- β -tocotrienol, d- γ -tocotrienol, dl- γ -tocotrienol, d- δ -tocotrienol, and dl- δ -tocotrienol. Two or more tocopherol compounds may also be used in combination. A substance called "mixed tocopherol (mixed tocopherol)" as a food additive, which is a mixture of d- α -tocopherol, d- β -tocopherol, d- γ -tocopherol, and d- δ -tocopherol as main components; the substance called "tocotrienol" is a mixture containing d- α -tocotrienol, d- β -tocotrienol, d- γ -tocotrienol and d- δ -tocotrienol as main components.

When the binder composition of the present invention contains a tocopherol compound, the content of the tocopherol compound is preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the copolymer.

Further, as other components, known additives such as a copolymerizable (meth) acrylic acid monomer containing an alkylene oxide (alkylene oxide), a (meth) acrylamide monomer, a dialkyl-substituted acrylamide monomer, a surfactant, a curing catalyst, a plasticizer, a filler, a curing inhibitor, a processing aid, an antioxidant, and the like can be appropriately blended. These may be used alone or in combination of two or more.

The copolymer as the main agent used in the adhesive composition of the present invention can be synthesized by copolymerizing (a) at least one of (meth) acrylate monomers having an alkyl group and a carbon number of C4 to C18 with (B) a hydroxyl group-containing copolymerizable monomer as a copolymerizable monomer group. The method of polymerizing the copolymer is not particularly limited, and an appropriate polymerization method such as solution polymerization or emulsion polymerization can be used.

In addition, the copolymer preferably includes at least one or more of a carboxyl group-containing monomer and a nitrogen-containing vinyl monomer containing no hydroxyl group as another copolymerizable monomer group.

The adhesive composition of the present invention can be prepared by blending (C) a bifunctional or higher isocyanate compound, (D) a crosslinking catalyst for a metal chelate compound, (E) a keto-enol tautomer compound, and further suitable optional additives into the above copolymer.

The copolymer is preferably an acrylic polymer, and preferably contains 50 to 100% by weight of a (meth) acrylate monomer or an acrylic monomer such as (meth) acrylic acid or (meth) acrylamides.

The acid value of the copolymer is preferably 8.0 or less, and more preferably 0.01 to 8.0. This improves the staining property and improves the performance of preventing the adhesive residue phenomenon.

Here, the "acid value" is one of the indexes indicating the acid content, and is expressed by mg of potassium hydroxide required for neutralizing 1g of a carboxyl group-containing polymer.

The adhesive layer obtained by crosslinking the adhesive composition preferably has an adhesive strength of 0.05 to 0.2N/25mm at a low peeling speed of 0.3m/min and an adhesive strength of 2.0N/25mm or less at a high peeling speed of 30 m/min. This makes it possible to obtain a performance that the change of the adhesive force with the peeling speed is small, and to quickly peel even in the case of high-speed peeling. Further, even when the surface protective film is temporarily peeled off for re-attachment, the surface protective film can be easily peeled off from the adherend without requiring an excessive force.

The gel fraction of the pressure-sensitive adhesive layer (crosslinked pressure-sensitive adhesive) obtained by crosslinking the pressure-sensitive adhesive composition of the present invention is preferably 90 to 100%. Since the gel fraction is so high, the adhesive force does not become excessively large at a low peeling rate, and the elution of unpolymerized monomers or oligomers from the copolymer is reduced, whereby the reworkability and the durability under high temperature/high humidity conditions can be improved, and the contamination of the adherend can be suppressed.

The adhesive film of the present invention is obtained by forming an adhesive layer on one side or both sides of a resin film, wherein the adhesive layer is obtained by crosslinking the adhesive composition of the present invention. The surface protective film of the present invention is obtained by forming an adhesive layer on one surface of a resin film, wherein the adhesive layer is obtained by crosslinking the adhesive composition of the present invention. Since the binder composition of the present invention is prepared by blending the components (a) to (E) in a well-balanced manner, the pot life is long and the crosslinking rate is high without using an organic tin compound. Therefore, the surface protective film of the present invention can be suitably used for a surface protective film for a polarizing plate, or for a surface protective film for any one of precision electrical/electronic parts selected from a group of precision electrical/electronic parts consisting of a flexible printed circuit board, a rigid printed circuit board, and a transparent conductive film.

In the adhesive film and the surface protective film of the present invention, a polyester film or the like can be used as a base material of a resin film or a release film (separator) for protecting an adhesive layer.

The resin film may be subjected to an anti-fouling treatment with a silicone-based or fluorine-based release agent, a coating agent, silica fine particles, or the like on the surface of the resin film opposite to the side on which the adhesive layer is formed, or may be subjected to an antistatic treatment by coating or mixing with an antistatic agent.

The release film is subjected to a release treatment with a silicone or fluorine-based release agent on the surface to be bonded to the adhesive surface of the adhesive layer.

Examples

The present invention will be specifically described below based on examples.

< production of acrylic copolymer >

[ example 1]

Nitrogen gas was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction tube, thereby replacing the air in the reaction apparatus with nitrogen gas. Then, 100 parts by weight of 2-ethylhexyl acrylate and 3.5 parts by weight of 8-hydroxyoctyl acrylate were charged into the reaction apparatus. Then, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and reacted at 65 ℃ for 6 hours to obtain an acrylic copolymer solution 1 having a weight average molecular weight of 50 ten thousand used in example 1. A part of the acrylic copolymer was taken and used as a sample for measuring an acid value described later.

Examples 2 to 6 and comparative examples 1 to 3

Acrylic copolymer solutions used in examples 2 to 6 and comparative examples 1 to 3 were obtained in the same manner as the acrylic copolymer solution 1 used in example 1, except that the respective monomer compositions were adjusted as described in (a), (B), and (I) in table 1.

< production of adhesive composition and surface protective film >

[ example 1]

After 6.0 parts by weight of acetylacetone was added to the acrylic copolymer solution 1 of example 1 prepared as described above and stirred, 1.5 parts by weight of Coronate HX (1256712525124931251254012512512512412512412588hx, isocyanurate of hexamethylene diisocyanate compound) and 0.05 parts by weight of tris (2, 4-pentanedionato) iron (III) were added and mixed with stirring to obtain an adhesive composition of example 1. The adhesive composition was applied to a release film composed of a polyethylene terephthalate (PET) film coated with a silicone resin, and then dried at 90 ℃ to remove the solvent, to obtain an adhesive sheet having an adhesive layer thickness of 25 μm.

Then, a polyethylene terephthalate (PET) film having one surface subjected to the antistatic treatment and the antifouling treatment was prepared, and an adhesive sheet was transferred to the surface of the polyethylene terephthalate (PET) film opposite to the surface subjected to the antistatic treatment and the antifouling treatment, to obtain the surface protective film of example 1 having a laminate structure of "PET film subjected to the antistatic treatment and the antifouling treatment/adhesive layer/release film (PET film coated with silicone resin)".

Examples 2 to 6 and comparative examples 1 to 3

Surface protective films of examples 2 to 6 and comparative examples 1 to 3 were obtained in the same manner as the surface protective film of example 1, except that the compositions of the respective additives were set as described in (C) to (E) of table 1.

TABLE 1

In Table 1, the parenthesized values indicate the weight parts obtained by setting the total weight of the group (A) to 100 parts by weight. In addition, the ratio of (E)/(D) is shown in table 2. In addition, compound names corresponding to abbreviations of the respective components used in table 1 are shown in table 3. Further, coronate (1246712525\\ 124931254088, registered trademark) HX, coronate HL, and Coronate L are trade names of japan Polyurethane Industry co (Nippon Polyurethane Industry co., ltd.); takenate (1247912465\124931254088, registered trade Mark) D-140N is the trade name of Mitsui chemical corporation; DURANATE (124871251712521\124931254088, registered trade mark) D101 is the trade name of Asahi Kasei Chemicals Corporation.

TABLE 2

	(E)/(D)
		Example 1	120
Example 2	85
		Example 3	300
Example 4	360
		Example 5	400
Example 6	500
		Comparative example 1	-
Comparative example 2	12
		Comparative example 3	3

TABLE 3

< test methods and evaluation >

The surface protective films of examples 1 to 6 and comparative examples 1 to 3 were aged for 7 days in an environment of 23 ℃ and 50% RH, and then the release film (PET film coated with silicone resin) was peeled off to expose the adhesive layer. The surface protective film with the adhesive layer exposed was bonded to the surface of the polarizer plate attached to the liquid crystal cell via the adhesive layer, left to stand for 1 day, then autoclaved at 50 ℃ under 5 atmospheres for 20 minutes, and further left to stand at room temperature for 12 hours, and the surface protective film thus obtained was used as a sample for measuring the adhesion.

< adhesion >

The measurement sample (a sample obtained by bonding a 25 mm-wide surface protective film to the surface of a polarizing plate) obtained above was peeled in the 180 ° direction at a low peeling speed (0.3 m/min) and a high peeling speed (30 m/min) by using a tensile tester, and the peel strength was measured and used as the adhesive strength.

< pot life >

The viscosity eta of the adhesive composition was measured immediately after blending the additives (C) to (E) ₀ (initial viscosity), and the viscosity η of the adhesive composition was measured after the adhesive composition was left to stand in a sealed state at 23 ℃ for 8 hours ₁ (viscosity after 8 hours). As an index of the pot life, the value of η was obtained ₀ Eta at 1.0 ₁ Value of (i), i.e. eta ₁ /η ₀ It is provided with and (4) a ratio. The evaluation target criteria are as follows: the viscosity after 8 hours was evaluated as "O" when it was less than 1.25 times the initial viscosity, and as "O" when it was 1.25 times or more and less than 1.50 times the initial viscosity"Δ", when gelation occurred by standing at 1.50 times or more or over 8 hours, was evaluated as "x".

The evaluation results are shown in table 4.

TABLE 4

The surface protective films of examples 1 to 6 had an adhesive force of 0.05 to 0.2N/25mm at a low peeling speed of 0.3m/min and an adhesive force of 2.0N/25mm or less at a high peeling speed of 30m/min, and had a sufficiently long pot life.

That is, the balance of adhesive force is excellent at a low peeling speed and a high peeling speed, and the storage life is long, and the properties as a surface protective film are also excellent.

In addition, the surface protective films of examples 1 to 6 were highly safe because the adhesive composition did not contain an organotin compound.

The surface protective film of comparative example 1 may not contain the bifunctional or higher isocyanate compound (C) as a crosslinking agent, and thus may have too large adhesive force at low peel speeds of 0.3m/min and high peel speeds of 30 m/min.

The surface protective film of comparative example 2 has a short pot life because the proportion of the (E) keto-enol tautomer compound relative to the (D) metal chelate crosslinking catalyst is small.

The surface protective film of comparative example 3 may not be coated because the pot life is too short because the proportion of the (E) keto-enol tautomer compound to the (D) metal chelate crosslinking catalyst is small, and crosslinking is performed before coating.

As described above, the surface protective films of comparative examples 1 to 3 cannot satisfy all the performance requirements such as excellent balance of adhesive force at low peeling speed and high peeling speed and long shelf life at the same time.

Claims

1. A surface protective film comprising a resin film and, formed on one surface thereof, an adhesive layer obtained by crosslinking an adhesive composition comprising an acrylic polymer and a crosslinking agent,

the acrylic polymer is a copolymer obtained by copolymerizing (A) at least one of (meth) acrylate monomers having an alkyl group and a carbon number of C4 to C18 with (B) a hydroxyl group-containing copolymerizable monomer as a copolymerizable monomer group, in such a manner that a polyalkylene glycol mono (meth) acrylate monomer is not contained,

the (B) hydroxyl group-containing copolymerizable monomer is at least one member selected from the group consisting of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-methylol (meth) acrylamide and N-hydroxyethyl (meth) acrylamide,

the hydroxyl group-containing copolymerizable monomer (B) is contained in a total amount of 0.1 to 10 parts by weight based on 100 parts by weight of the acrylic polymer, and 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate among the hydroxyl group-containing copolymerizable monomers (B) are contained in a total amount of 0.1 to 5.0X 100/105.2 parts by weight,

the adhesive composition contains the following substances in the following proportions relative to 100 parts by weight of the acrylic polymer: 0.1 to 10 parts by weight of (C) a bifunctional or higher isocyanate compound, (D) 0.001 to 0.5 part by weight of a metal chelate crosslinking catalyst, and (E) 6.0X 100/103.5 to 20X 100/105.5 parts by weight of a keto-enol tautomer compound as the crosslinking agent,

the ratio of the (E)/the (D) by weight is 80 to 1000,

the metal chelate is at least one selected from the group consisting of tris (2, 4-pentanedionato) iron (III), titanium triacetylacetonate, ruthenium triacetylacetonate, zinc diacetoacetonate, aluminum triacetylacetonate, zirconium tetraacetoacetonate, tris (2, 4-hexanedionato) iron (III), bis (2, 4-hexanedionato) zinc, tris (2, 4-hexanedionato) titanium, tris (2, 4-hexanedionato) aluminum, and tetrakis (2, 4-hexanedionato) zirconium,

the adhesive composition does not contain an organotin compound and a polyether-modified siloxane compound as the crosslinking catalyst,

the adhesive composition further contains 0.01 to 5 parts by weight of a tocopherol compound as an antioxidant per 100 parts by weight of the acrylic polymer,

the tocopherol compound is at least one selected from the group consisting of d-alpha-tocopherol, dl-alpha-tocopherol, d-beta-tocopherol, dl-beta-tocopherol, d-gamma-tocopherol, dl-gamma-tocopherol, d-delta-tocopherol, dl-delta-tocopherol, d-alpha-tocotrienol, dl-alpha-tocotrienol, d-beta-tocotrienol, dl-beta-tocotrienol, d-gamma-tocotrienol, dl-gamma-tocotrienol, d-delta-tocotrienol, and dl-delta-tocotrienol,

the viscosity of the adhesive composition after storage at 23 ℃ for 8 hours after the blending of the adhesive composition is lower than 1.25 times of the viscosity immediately after the blending,

the adhesive layer has an adhesive strength of 0.05 to 0.2N/25mm at a low peeling speed of 0.3m/min and an adhesive strength of 2.0N/25mm or less at a high peeling speed of 30 m/min.

2. The surface protective film according to claim 1,

among the (C) bifunctional or higher isocyanate compounds, the bifunctional isocyanate compound is a non-cyclic aliphatic isocyanate compound and is a compound produced by reacting a diisocyanate compound with a diol compound,

the diisocyanate compound is an aliphatic diisocyanate, is one selected from the group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and lysine diisocyanate,

the diol compound is one selected from the group consisting of 2-methyl-1, 3-propanediol, 2-dimethyl-1, 3-propanediol, 2-methyl-2-propyl-1, 3-propanediol, 2-ethyl-2-butyl-1, 3-propanediol, 3-methyl-1, 5-pentanediol, 2-dimethyl-1, 3-propanediol monohydroxypivalate, polyethylene glycol and polypropylene glycol,

in the (C) bifunctional or higher isocyanate compound, the trifunctional isocyanate compound is isocyanurate of hexamethylene diisocyanate compound, isocyanurate of isophorone diisocyanate compound, adduct of hexamethylene diisocyanate compound, adduct of isophorone diisocyanate compound, biuret of hexamethylene diisocyanate compound, biuret of isophorone diisocyanate compound, isocyanurate of toluene diisocyanate compound, isocyanurate of xylylene diisocyanate compound, isocyanurate of hydrogenated xylylene diisocyanate compound, adduct of toluene diisocyanate compound, adduct of xylylene diisocyanate compound, adduct of hydrogenated xylylene diisocyanate compound.

3. The surface protective film according to claim 1 or 2, wherein the copolymer is an acrylic polymer comprising at least one or more of a carboxyl group-containing monomer and a nitrogen-containing vinyl monomer containing no hydroxyl group as another copolymerizable monomer group.

4. The surface protective film according to claim 1 or 2, wherein the gel fraction of the adhesive layer obtained by crosslinking the adhesive composition is 90 to 100%.

5. The surface protective film according to claim 1 or 2, which is used as a surface protective film for a polarizing plate.

6. The surface protective film according to claim 1 or 2, which is used for the purpose of a surface protective film for a precision electrical/electronic component selected from any one of a group of precision electrical/electronic components consisting of a flexible printed circuit board, a rigid printed circuit board and a transparent conductive film.